Apparatus for collecting and discharging waste material is known utilizing two cooperating sets of moving toothed structures, each being provided with plate-like teeth lying in parllel planes parallel to the direction of motion, and spaced, on each structure, at intervals perpendicular to those planes. The teeth of both structures are mutually intercalated in a collection zone where they are both moving in the same direction and, at positions remote from the collection zone, both structures interact with stationary combs comprising sets of blades which lie between adjacent lines of teeth, closely fitting against the sides of the teeth and their separating means to remove matter trapped between the teeth or adhering to the sides thereof. Means are also provided whereby the toothed structures, together with their comb assemblies, may become separated to permit the passage of matter which is too tough or bulky to be shredded by the teeth.
Both toothed structures may take the form of rotatably mounted shafts carrying assemblies of thin metal disc with circumferentially formed teeth, the discs being separated by relatively thick plain discs of diameter somewhat less than that at the tooth roots, all members being clamped together so that the assembly rotates as an integral unit.
Alternatively, one of the structure may be a shaft assembly as described and the other a belt type conveyor bearing lines of teeth at intervals across its width.
The foregoing structures are shown in Byers U.S. Pat. No. 4,336,137 and United Kingdom Patent No. 2,061,752 to the present inventor.
Although teeth of almost any conceivable shape may be used to create an entrapment and collecting action, difficulties arise with the prior art apparatus, e.g. as disclosed in the above mentioned patents, as the spoil enters the separating scraper zone because of the generation of a biting action on the material developed between the disc teeth and separator combs as the teeth move relative to the combs. If the parts are not sufficiently robust or the driving force is inadequate, this biting action will defeat the objective of the separator combs and result in either the machine breaking or jamming even when dealing with soft materials such as cordage or plastic bags.